This invention relates to closures, and more particularly to a closure such as a door comprising glass in a frame subject to cold air on one side and warmer humid air on the other.
The invention is especially concerned with a glass door for a refrigerator or freezer, more particularly a refrigerator or freezer such as is used in retail food stores, being of glass for viewing the contents of the refrigerator or freezer. Such doors as heretofore supplied on refrigerators and freezers manufactured by Universal Nolin Division of the assignee of this invention have comprised double-pane or triple-pane glass in a metal (aluminum) frame, the frame being made of metal for structural integrity of the completed door assembly. These doors are subject to cold air from the refrigerator or freezer on the inside or rear, and warmer air (which is often quite humid) on the outside or front. While the metal (aluminum) may be covered in some fashion in an attempt to minimize condensation of moisture on the exposed surfaces of the frame (the warm side surfaces), it has generally been found necessary for effectively inhibiting condensation to incorporate an electrical resistance heating wire or wires in the frame to keep it warm for this purpose. This not only adds to the cost of the door, but also imposes additional costs for operation of the refrigerator or freezer on account of the electrical power consumption for warming the frame. In a typical situation this power consumption is 65 watts per door, which equals 1.6 KWH a day, and at an average KWH cost of about 7.cent., this amounts to $80 per year for a 2-door cabinet just to warm the door frames.